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Replace bottom cover?
- Thread starter creeman
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I've always questioned this myself. A touch-up, even on anodized surfaces, which is done correctly can still carry significant adhesion. It will, as noted, not be as durable as the original however. Keep in mind that with deep scratches, the outer coating is removed.
http://www.gwp-ag.com/media/www.gwp-ag.com/org/med_645/1563_hard-anodizing-alloys.pdf
The unibody aluminum material does not seem to fall into the acceptable anodizing standards and the coating on it is very similar to some aluminum powder coatings. Also, it comes off pretty easily for some users.
The chart you provided was for Hard Anodizing. The listed were extrusion, diecasting and sand casting. Apple probably uses a 6061 Alloy of aluminum, also about all aluminum has the ability to be anodized...especially the common 6061. And the unibody is a billet, not a casting.
Nevermind, price=ignored. And its ANODIZED, not PAINTED. Anodizing is a chemical plating process.
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Yes, the MacBook Pro, MacBook Air, and iPad are all constructed from the same outer material; which is anodized aluminum.
I thought that some aluminum was rarely anodized due to corrosion issues, especially organic based? I thought that billet usually started out as casting and that aluminum anodizing of billet/casting were quite similar? 6061 is the 'standard' "airplane grade" aluminum, correct?
Almost all aluminum that needs a durable coating is anodized as this is really the only way to apply a significant Rockwell or Brinell hardness to aluminum. The billet they use would be extruded then formed by rolling into shape. 6061 is the most common general purpose alloy. http://en.wikipedia.org/wiki/6061_aluminium_alloy
6061 also precipitate hardens to degree where you can heat it to Below Critical Temp and either keep it there for a period or cool it rapidly or slowly depending on the alloy to achieve some hardness. You will not achieve anything near a steel with above .4% carbon like a 4140 chromoly or by carburizing 1018 to get a hardface approximately .060" thick as both of these methods will produce a C60 rockwell easily and then tempered to a 45-55 range to remove some of the brittleness. While HARD anodizing will produce somewhere near a C65-70 Rockwell, but it is hard to measure due to its only about .002"-.003" thick(a human hair/piece of copy paper are about .004" thick) and the Diamond penetrator of the Rockwell C scale will not effectively measure the surface and will instead blow through the source material(aluminum) which is closer to a C35 rockwell. Also the C65-70 layer is very thin and very brittle, not good to protect against impact but more of an abrasion/scratch resistant layer and also protects the aluminum from oxidation.
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Thank you. Very cool to learn. I'm big on pocket knives and some use aluminum handles (ti is more common in high end ones). I always figured aluminum would be able to have a better combo of weight-strength-brittleness than most steels and anodizing for stronger scratch and abrasion resistance makes a lot of sense. I suppose for touch-up then the best material would be an expanding epoxy base. Obviously, it won't be near as tough as the anodized portion, but it would probably hold up to normal use. Given the OP has numerous scratches, a clear bottom case would be a good call and would also help keep the touch-up on. Also, whatever medium is used to fill the scratch, I guess getting one designed for temp flux may be a good call.
This will sound crazy but I was playing with JD Quick Weld and I got the color pretty close. I painted some on a piece of cardboard too see how tough it is upon drying as it isn't quite the recommended 50/50 mixture.
Kind of OT but I have one pocket knife with a hybrid tool steel that has been tested to be at least 67 and some are in the 70s Rockwell Hardness!
I'm too scared to give it 'chopping' use due to brittleness, but a lot of people say it is no more brittle than M2HS.
Thank you. Very cool to learn. I'm big on pocket knives and some use aluminum handles (ti is more common in high end ones). I always figured aluminum would be able to have a better combo of weight-strength-brittleness than most steels and anodizing for stronger scratch and abrasion resistance makes a lot of sense. I suppose for touch-up then the best material would be an expanding epoxy base. Obviously, it won't be near as tough as the anodized portion, but it would probably hold up to normal use. Given the OP has numerous scratches, a clear bottom case would be a good call and would also help keep the touch-up on. Also, whatever medium is used to fill the scratch, I guess getting one designed for temp flux may be a good call.
This will sound crazy but I was playing with JD Quick Weld and I got the color pretty close. I painted some on a piece of cardboard too see how tough it is upon drying as it isn't quite the recommended 50/50 mixture.
Kind of OT but I have one pocket knife with a hybrid tool steel that has been tested to be at least 67 and some are in the 70s Rockwell Hardness!
I'm too scared to give it 'chopping' use due to brittleness, but a lot of people say it is no more brittle than M2HS.
I've tried JB Weld on my truck mirror to hold a bolt back into the plastic, needless to say I was at a gas station checking a nice looking woman out and closed the door and the mirror fell off... Doesn't seem to take temp changes well or adhere to anything smooth very well, may differ for you.
Also is the Hybrid stell your talking about called Damascus?
The original JD Weld I have used with success on some car manifolds and intercooler plumbing..with that said, I've noticed it has an exceptional set time of at least 12 hours and an actual dry time of a few days. Cold slows it down even more. The JB Quick has a much faster set time although it is not as strong. With that said, if I was watching a hot lady in my mirror and it fell off, I would never use the product again and I would complain until the company got me a poster of Niki Ziering.
I have a Damascus knife which is from a WWI German tank's barrel and IIRC it is rated as 67-69. The one which has gotten to the low 70s is ZDP-189 used by Spyderco, William Henry and a few others. They generally rate it around 66-69, but individual tests have seen higher. I've been told some D2 has gotten up to 68-69, but I imagine it becomes very brittle. I am really excited about the CPM-M4 high speed tool steel which is starting to show up in many knives with a hardness in the mid 60s, but without any more brittleness than normal tool steels (used for knives) at low 60s. Most of the knives I carry are made by Chris Reeve who uses S30V at about 59 Rc; I like it for the impact resistance, ease to sharpen, corrosion resistance, and that the Reeves (Sebenza, Mnandi, and Umnumzaan) are IMO the best pocket knives ever made. Supposedly he is working with Crucible on a newer type of steel that is far harder and will be one of the toughest steels ever used on a pocket knife by a mainstream company. I've also read that some small companies have been playing with titanium-tungsten-carbide-alloy or something really long and whacky like that and have seen hardness that is hundreds of times harder than the hardest tool steels; but it is more brittle than ceramic so its value to knives are limited and its costs to make will probably keep it as more of a concept than a trend.